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Old 29-03-2019, 11:07   #1
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Riding out a storm, sealed up tight down below. Watch out for CO2.

I've twice found myself sealed up tight down below with other crew. All hatches closed, dorades plugged, all vents sealed; to prevent water ingress from a knockdown or roll.

I noticed people having problems with decision making, and generally just becoming progressively dumber. I ascribed it to fatigue. But maybe I was at least partially wrong.

Here's an interesting experiment that shows a cognitive decline at CO2 levels as low as 1,000 parts per million (PPM), and to the point of mental dysfunction with CO2 levels as low as 2,500 PPM. https://ehp.niehs.nih.gov/doi/10.1289/ehp.1104789.

The ambient outdoor level is about 410 PPM (and getting higher as time goes on).

I was taught that crew (sealed in a long metal tube under water...) shouldn't expect symptoms of hypercarbia until the concentration is over 10,000 PPM (1%) -- that's about the threshold where some people first experience a headache. But I don't know if the cognitive effects were ever considered in that number.

Short of installing CO2 scrubbers, I don't know how to solve that problem except to periodically air out the cabin, and risk taking on water. There are CO2 monitors on the market that cost around $100. I'm going to put one in my cabin.
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Old 29-03-2019, 12:16   #2
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Re: Riding out a storm, sealed up tight down below. Watch out for CO2.

Yes low O2 is just as important as propane/hydrocarbon fumes and CO detection.
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Old 29-03-2019, 13:53   #3
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Re: Riding out a storm, sealed up tight down below. Watch out for CO2.

Please be very careful with reporting numbers and suppositions and the need for countermeasures. There are countless things that you can do to people to cause a transient degradation of cognitive performance on finite testing that have no real-world applicability. The #1 and #2 causes of transient degradation is sleep deprivation or stress. #3 is a distant third and is not C02. Drugs, alcohol, sleep apnea, mental health issues issues notwithstanding.

If it helps, astronauts live in a 5,000-7,000ppm C02 environment even though it has long been recognized that C02 has performance degradation at these levels. On a boat, you just crack the window for a minute, case closed. People are born with C02 sensors that causes them to take appropriate countermeasure on their own while also having compensatory mechanisms to deal with the high C02 state associated with being stuck in a boat in a storm. If you have a problem with those systems you're either already dead or know about it already.
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Old 29-03-2019, 14:18   #4
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Re: Riding out a storm, sealed up tight down below. Watch out for CO2.

I am not clear why one would seal up the dorades. The amount of water that may come in is so small and manageable, it seems to be of no benefit relative to the risk of running out of oxygen and/or build up of CO2.
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Old 29-03-2019, 14:23   #5
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Re: Riding out a storm, sealed up tight down below. Watch out for CO2.

I know from personal experience that seasickness can make you very stupid. Not to mention headaches, nausea, and so on.
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Old 29-03-2019, 14:29   #6
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Re: Riding out a storm, sealed up tight down below. Watch out for CO2.

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I am not clear why one would seal up the dorades. The amount of water that may come in is so small and manageable, it seems to be of no benefit relative to the risk of running out of oxygen and/or build up of CO2.
I take off my dorado scoops and put in the plates if I'm taking a long passage offshore. A 4" dorade can in theory let in 250 gallons/min. So if you roll and stay capsized, with two dorades, within two minutes you could be looking at 1000 gallons in the boat or 8000 pounds of water. Of course it's going to be a lot less than that, practically speaking, but they are holes in the boat.

Overly cautious? I'd rather minimize risk and leave one less thing to do if the weather turns bad, and just open some port lights/hatches occasionally for air circulation.
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Old 29-03-2019, 14:41   #7
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Re: Riding out a storm, sealed up tight down below. Watch out for CO2.

I wonder why you close dorade boxes ??? Mine they don't leak at all , and even if the boat capsize the water intrusion for then will be little .

That being said when I had only one Dorado box I found the ventilation insufficient with 4 people inside.
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Old 29-03-2019, 15:17   #8
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Re: Riding out a storm, sealed up tight down below. Watch out for CO2.

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I am not clear why one would seal up the dorades. The amount of water that may come in is so small and manageable, it seems to be of no benefit relative to the risk of running out of oxygen and/or build up of CO2.

They admit water when the vents are submerged and the vessel heels past about 90 degrees. These were storm conditions where a knock down or temporary inversion (roll/partial roll) was a possibility.
See also reply 6 below.
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Old 29-03-2019, 15:24   #9
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Re: Riding out a storm, sealed up tight down below. Watch out for CO2.

But the fact that air is not escaping when the boat is capsized , doesn't eliminate the water intrusion ??
I have had 1 one knockdown no water came from the dorado box 90 deegrees water doesn't reach it
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Old 29-03-2019, 15:34   #10
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Re: Riding out a storm, sealed up tight down below. Watch out for CO2.

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Please be very careful with reporting numbers and suppositions and the need for countermeasures. There are countless things that you can do to people to cause a transient degradation of cognitive performance on finite testing that have no real-world applicability. The #1 and #2 causes of transient degradation is sleep deprivation or stress. #3 is a distant third and is not C02. Drugs, alcohol, sleep apnea, mental health issues issues notwithstanding.

If it helps, astronauts live in a 5,000-7,000ppm C02 environment even though it has long been recognized that C02 has performance degradation at these levels. On a boat, you just crack the window for a minute, case closed. People are born with C02 sensors that causes them to take appropriate countermeasure on their own while also having compensatory mechanisms to deal with the high C02 state associated with being stuck in a boat in a storm. If you have a problem with those systems you're either already dead or know about it already.

I'm reporting on a scientific paper. Not suppositions. Of course, I can't vouch for the quality of the research - I wasn't there. And, like every research paper ever written, the report ends by saying additional research is needed (how else to get follow-on grants?). Just like you, I too recommend airing out the cabin as a countermeasure ("crack a window"). If the problem isn't hypercarbia, that action will do no harm - except maybe admit some seawater.

I appreciate your argument, but it's conclusions are better taken up with the authors of the paper. My intention is only to share that paper because it might be interesting and instructive.

At 2,500 PPM, I doubt many people would recognize the need to take action to get fresh air because the overt symptoms, if any, resemble those from other causes (seasickness, etc.), as you point out. And I know from personal experience and training that just gradually becoming stupid, as one does from hypoxia, and here reportedly also from hypercarbia, isn't enough to spur action. A person has to recognize the cause of a problem before taking appropriate action. Get some air before reaching for the seasickness pills.

In a confined space at one atmosphere of pressure hypercarbia (too much CO2) sets in before hypoxia (too little O2).

I was completely unaware of any cognitive effects from low levels of CO2, so the information is new and useful to me. As I hope it will be to someone else.

As for NASA's tolerance to CO2 exposure in astronauts on ISS, I suggests reading this: https://thinkprogress.org/its-taking...s-7af09e82b83/

and this: https://thinkprogress.org/exclusive-...-2748e7378941/
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Old 29-03-2019, 16:30   #11
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Re: Riding out a storm, sealed up tight down below. Watch out for CO2.

Do not assume the amount of water coming in through a dorade is only small. They work find for spray and green water, but a knockdown or capsize is different.

We had a 4" one on the boat we had the knockdown in, and it let in a fair amount--I plugged it with a dishtowel before we righted. if upside down, instead of mast in water, I suspect Suijin has the right of it, and 250 gallons per minute is not to be sneezed at. As long as one is undamaged, they can be plugged pretty quick, though, and we like having the fresh air come in.

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Old 29-03-2019, 16:53   #12
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Re: Riding out a storm, sealed up tight down below. Watch out for CO2.

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Originally Posted by Cpt Pat View Post

Short of installing CO2 scrubbers, I don't know how to solve that problem except to periodically air out the cabin, and risk taking on water. There are CO2 monitors on the market that cost around $100. I'm going to put one in my cabin.
Interesting point, that may be more of a modern problem as we can now monitor electronically from below, via AIS and Radar

In the 80's when hove to in extreme storm conditions I posted an experienced lookout, BT the most protected hatch, (usually behind some kind of deck structure where
At the top of crests, he will pop his head out for a quick scan and of course, we got a rapid air exchange
100nm off the Oregon coast in December, we did not have to worry about CO2
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Old 29-03-2019, 17:26   #13
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Re: Riding out a storm, sealed up tight down below. Watch out for CO2.

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At 2,500 PPM, I doubt many people would recognize the need to take action to get fresh air because the overt symptoms, if any, resemble those from other causes (seasickness, etc.), as you point out. And I know from personal experience and training that just gradually becoming stupid, as one does from hypoxia, and here reportedly also from hypercarbia, isn't enough to spur action. A person has to recognize the cause of a problem before taking appropriate action.
Forget ppm/cognitive for a minute. No need to type out numbers in response, but at minimum consider this conceptually to see if we can remedy a concern.

Assuming that you're of average/normal health...what do you think the dissolved blood gas situation right now is in your own blood? Your own CO2 and bicarb level?

What is it in the morning for a obese chain-smoker who has severe sleep apnea with mild-moderate copd, doesn't use cpap, but still works as a truck driver? (this is a lot of people)

You have concern that an otherwise healthy person on a sailboat will become stuporous, unable to recognize that they need to do something with the air situation because the boat is closed up for a storm.

Around about what blood CO2 and bicarb level are you thinking that this "healthy yesterday but now, day 1-3 (your choice) in the sailboat during a storm might pass out because of CO2 levels" person might have? I'm not asking about ambient partial pressures/ppm, I'm asking about our sailor in presumed peril's blood gasses. In your personal experience and training what are they...or do they not matter for some reason?
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Old 29-03-2019, 17:56   #14
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Re: Riding out a storm, sealed up tight down below. Watch out for CO2.

who said anything about passing out?

putting in an appropriate meter / alarm is not drastic

no one is saying everyone should do it

but certainly worth a hmm something to consider
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Old 29-03-2019, 18:58   #15
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Re: Riding out a storm, sealed up tight down below. Watch out for CO2.

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who said anything about passing out?

putting in an appropriate meter / alarm is not drastic

no one is saying everyone should do it

but certainly worth a hmm something to consider
I understood the concern to be that the sailor may become stuporous, unable to recognize a problem, unable to do something about it, and succumb to the effects of hypercapnia.

I don't know the exact number, but I'd guesstimate that 5-10% of healthcare spending is borne by something that someone read on the internet. That's about 1% of GDP. When the NNT for an intervention is high...this is money wasted at a presumable opportunity cost of problems with a lower NNT. Where the NNT is infinite while the NNH is any real number, then the intervention is declared outright more likely to harm.

It's otherwise inconceivable to me...even if C02 was a problem...that someone would not stick their head outside every xx minutes to survey the scene, even for a few seconds...no less probably get out checking for chafe (don't know the boat/circumstances). In a mild breeze this ordinarily will produce a good air exchange. In a blow no doubt.
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